Download Skeletal – Part 4

Skeletal
PART 5
Vertebral Column (Spine)
 Vertebral Column (Spine) –
Serves as the axial support of
the body


Extends from the skull (which it
supports) to the pelvis, where it
transmits the weight of the body to
the lower limbs.
Formed from 26 irregular bones
connected and reinforced by
ligaments in such a way that a
flexible, curved structure results.
Vertebrae
 Before birth, the spine consists of 33 separate
bones called vertebrae.

But 9 of these eventually fuse, forming the two composite
bones, the sacrum and the coccyx, which construct the
inferior portion of the vertebral column.
 Sacrum
– Located below the
lumbar vertebrae; Made up of
five fused vertebrae.
 Coccyx – Located below the
sacrum; made up of 4 fused
vertebrae.
Vertebrae
 Of the 24 single bones:



Cervical Vertebrae – 7
vertebrae of the neck.
Thoracic Vertebrae – Next 12
vertebrae; midsection of the
back.
Lumbar Vertebrae –
Remaining 5 vertebrae
supporting the lower back.
 Remembering common
meal times (7 a.m., 12 noon,
and 5 p.m.) may help you
recall the number of bones
in these 3 regions!
Intervertebral Discs
 Intervertebral Discs –
Pads of flexible fibrocartilage that separate
single vertebrae.


Cushion the vertebrae and
absorb shock.
Change over age:
In a young person, the discs
have high water content
(90%) and are spongy and
compressible.
 As a person ages, the water
content of the discs decreases
(as it does in other tissues
throughout the body), and the
discs become harder and less
compressible.

Herniated Discs
 Herniated Discs –
Slipped intervertebral
discs.

Older people are more
predisposed to herniated
discs since the following occur:
1.
2.

Drying of the discs
Weakening of the ligaments of the vertebral column
If the protruding disc presses on the spinal cord or the
spinal nerves exiting from the cord, numbness and
excruciating pain can occur.
Spinal Curvature
 The discs and the S -
shaped structure of the
vertebral column work
together to:
1.
2.
Prevent shock to the head
when we walk or run.
Make the body trunk
flexible.
Abnormal Spinal Curvatures
 There are three types of
abnormal spinal
curvatures:
1.
2.
3.
Scoliosis
Kyphosis
Lordosis
 May be congenital or a
result from disease,
poor
posture,
or
unequal muscle pull on
the spine.
Cervical Vertebrae
 The 7 cervical vertebrae
form the neck region of
the spine.
 The first two vertebrae
(atlas and axis) are
different because they
perform functions not
shared by the other
cervical vertebrae.
The Atlas (C1)
 The Atlas (C1):
 Has no body.
 The superior surfaces of its
transverse processes
contain large depressions
that receive the occipital
condyles of the skull.
 This
joint allows you to
nod “yes.”
The Axis (C2)
 The Axis (C2):
 Acts as a pivot for the rotation
of the atlas and skull above.
 It
has a large, upright process,
the odontoid process (or dens),
which acts as the pivot point.
 The joint between C1
and C2 allows you to
rotate your head from
side to side to indicate
“no.”
“Typical” Cervical Vertebrae
 Includes C3 through C7.
 They are the smallest,
lightest vertebrae.
 Spinous processes:

Short and divided into two
branches.
 Transverse processes:
 Contain foramina (openings)
through which the vertebral
arteries pass on their way to the brain above.

Any time you see these foramina in a vertebra, you should know
immediately that it is a cervical vertebra.
Thoracic Vertebra
 The 12 thoracic vertebrae (T1-
T12) are all typical.
 They are larger then cervical
vertebrae.
 The body:


Somewhat heart-shaped.
Has two costal demifacets
(articulating surfaces) on each side,
which receive the heads of the ribs.
 The spinous process:

Long and hooks sharply
downward, causing the vertebra to
look like a giraffe’s head viewed
from the side.
Lumbar Vertebrae
 The five lumbar vertebrae
(L1-L5) have massive,
blocklike bodies.
 Since most of the stress on
the vertebral column
occurs in the lumbar
region, these are the
sturdiest of the vertebrae.
 Spinous processes:

Short, hatchet-shaped, makes
them look like a moose head
from the lateral aspect.
The Sacrum
 The sacrum is formed
by the fusion of five
vertebrae.
 It lies between L5 and
the coccyx.
 The winglike alae
articulate laterally with
the hip bones, forming
the sacroiliac joints.
The Sacrum
 The sacrum forms
the posterior wall
of the pelvis.
 The vertebral canal
continues inside
the sacrum as the
sacral canal.
Coccyx
 The coccyx is formed
from the fusion of 3-5
tiny, irregularly
shaped vertebrae.
 It is the human
“tailbone,” a remnant
of the tail that other
vertebrate animals
have.